Open Radar

 
11-Feb-2013 04:06 PM Rainer Müller:
Summary:

The implementation of BSD grep in /usr/bin/grep does not handle the combination of the -m with one of the -A/-C flags correctly. Instead of printing the after context for the last match, it exits prematurely.

Steps to Reproduce:

Use /usr/bin/grep with arguments -A or -C which are meant to output context after or around the match and additionally use -m to limit the total number of matches. For the last match hitting the given limit no after context is printed.

Here is a comparison of the behavior with GNU grep installed from MacPorts:

$ /usr/bin/grep --version
grep (BSD grep) 2.5.1-FreeBSD
$ /opt/local/bin/grep --version |head -n1
/opt/local/bin/grep (GNU grep) 2.14
$ echo -e "Foo\nBar\nBaz\n" | /usr/bin/grep -m1 -A2 Foo
Foo
$ echo -e "Foo\nBar\nBaz\n" | /opt/local/bin/grep -m1 -A2 Foo
Foo
Bar
Baz
$ echo -e "Foo\nBar\nBaz\n" | /usr/bin/grep -m1 -C1 Bar
Foo
Bar
$ echo -e "Foo\nBar\nBaz\n" | /opt/local/bin/grep -m1 -C1 Bar
Foo
Bar
Baz
$

Expected Results:

BSD grep should return the same result as GNU grep in the examples above.

Actual Results:

The context after the match is missing from the output.

Regression:

This is a regression as the behavior of /usr/bin/grep is different to the behavior of GNU grep, which was shipped in previous versions of Mac OS X.